According to population statistics of 1936,
the then Kuomintang Republic of China had an estimated
48,104,240 Muslims. Below is a reference from about the Muslim
population before Communist Revolution:

Under the pretext of unification of national
education, Islamic schools were closed and their students
transferred to other schools which taught only Marxism and
Maoism. Other outrages included the closing of over 29,000
mosques, the widespread torture of imams, and executions of over
360,000 Muslims. Aside from the physical annihilation, Muslims
have been subjected to a constant attack on their Islamic
identity especially during the so-called Cultural Revolution
(1966-76). For instance, posters which appeared in Peking (later
to be called Beijing) in 1966, openly called for the abolition
of Islamic practices. Muslims were also barred from learning
their written language which incorporated the Arabic script and
was influenced by Arabic, Turkish and Farsi. This change was
critical as it distanced Muslims from the Arabic language, the
language of the Qur'an and their Islamic aspirations. During
this era many Mosques were closed down and waqf properties were
confiscated. (Yusuf Abdur Rahman)

Since religious freedom was declared in 1978,
the Chinese Muslims have not wasted time in expressing their
convictions. There has been an increased upsurge in Islamic
expression in China, and many nationwide Islamic associations
have been organized to coordinate inter-ethnic activities among
Muslims. Islamic literature can be found quite easily and there
are currently some eight different translations of the Qur'an in
the Chinese language as well as translations in Uygur and the
other Turkic languages (Yusuf Abdul Rahman). There are now some
34,000 mosques and 400 Islamic organization in the entire
People's Republic of China (Beijing, Rabi Awwal 28/June 20 (IINA).
Muslims are allowed to perform Hajj and the number of pilgrimage
from China is about 3000 per year.

At present, according to official statistics
there are 28 million Muslim in China but in1936 it was estimated
that the Muslim population was 48 million. By this time total
population has increased 3-4 fold. So we can conclude that the
total Muslim population has increased minimum by that same
proportion. Therefore, now the total Muslim population is at
least 150 million.